The present disclosure relates to hearing technology, and more particularly, to a method and system for determining the occlusion effect in an earpiece.
In the fitting of hearing protection devices (HPD), measurements are made of the attenuation provided by the HPD as well as whether there is any occlusion effect due to the actual earpiece of the HPD. Occlusion effect, or additional noise heard by the HPD user due to the user's voice bouncing off the earpiece of the HPD, may be bothersome to the user. Measurement of attenuation is typically done by measuring the sound pressure level (SPL) on the outer side of the ear canal open to the air and comparing it to the SPL measured on the inner side of the ear canal blocked by the HPD.
The occlusion effect is typically measured by comparing SPLs generated by the wearer's voice, for example, within the ear canal without the earpiece with the SPLs generated within the ear canal with the earpiece in place. These sound pressure differences provide an indication of the degree of occlusion provided by the earpiece. The term “degree of occlusion” is used to refer to the degree to which an occluding object, such as an earpiece, prevents leakage and/or inhibits occlusion effect. In most instances, the measured difference between the SPLs described above provide a quantitative measure of the degree of occlusion of an occluding object.
The failure of an earpiece to properly seal and fit within the ear canal of a subject can result in unwanted repercussions. Without a close fit between the earpiece and the ear canal wall, excessive leakage may result. This excessive leakage may result in reducing the effectiveness of the HPD. With respect to occlusion effect, the bone conduction of the wearer's voice may be amplified when the ear is occluded. The HPD wearer's own voice is thus heard as being loud and distorted. This effect was noted by J. Zwislocki in his article entitled “Acoustic Attenuation Between The Ears”, J. Acous. Soc. Amer. 25:752-759 (1953). The value of deeply sealed earpieces to eliminate this effect is discussed in an article by Mead Killion entitled “The ‘Hollow Voice’ Occlusion Effect” Hearing Aid Fitting—Theoretical and Practical Views, CH. III, pp. 231-242 (1988). It is therefore important in some fittings to ensure that the earpiece seal extends far enough into the ear canal to eliminate this occlusion effect.
Further limitations and disadvantages of conventional and traditional approaches to measuring occlusion effect will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present disclosure as set forth in the remainder of the present application with reference to the drawings.